Flora of North America species comparison

Papaver californicum grows in central western and southwestern California in the Coast, Transverse, and Peninsular ranges. This is the only caulescent poppy, and the only annual one, native to the flora. In the past it has been included in Papaver sect. Rhoeadium, together with the other annuals that have glabrous capsules and distal leaves not clasping, which are native to Eurasia. Recently, based on differences in filament color, stigmatic disc shape, and capsule dehiscence, J. W. Kadereit (1988b) assigned P. californicum to a new monotypic section and suggested that it originated from the same stock as the perennial, scapose, arctic-alpine poppies (Papaver sect. Meconella).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

In its native range, Papaver dubium is a tetraploid complex of five subspecies whose morphologies and distributions intersect to a considerable degree (J. W. Kadereit 1989, 1990). Probably several, if not all, of these entities have been introduced in North America, but it is fruitless to try to distinguish them here, where the species has arrived as a crop weed and the subspecies have no geographic integrity.

Papaver dubium sometimes seems to intergrade with P. rhoeas, at least in North America. The most readily evident character for distinguishing them reliably is the nature of the distal pubescence on the peduncles–whether spreading or appressed.

(Discussion copyrighted by Flora of North America; reprinted with permission.)